Mobile app maker Frengo is now making apps for popular social networks (Facebook, Hi5, etc.) that allow connections between networks. The Flirtable app, for example, allows users on one social network to flirt with users on another. The Lolz app, likewise, lets users share LOLcat images (sadly, not very funny ones) across networks.
Frengo is using OpenSocial as a standard for building the apps, but OpenSocial doesn't address friend portability or cross-network messaging. Frengo is building that capability into its widgets so that a user on a smaller network who adds one of its apps will join the ad-hoc group of users from other networks that are using the same app elsewhere.
For example, when you use the Flirtable dating app, you're accessing all the app's users no matter what network they're on. In a very cool twist, if you use the Flirtable app to send a message or a gift to another user, that communication can reach their social profile page (usually, their "wall") even if they're on another network from you.
CEO Mahi de Silva admits that "What we do may not appear to be aligned with the business goals of social networks." Frengo loosens up the lock-in of social networks. De Silva believes that what Frengo does is still within the terms of service of the social networks, if only just. And users would probably agree with de Silva that connecting social networks together raises the value of all of them -- even the big networks that would appear to have the most to lose.
I'm happy to see efforts like this, since they make social apps more about people, less about the companies running their networks. And I think many execs at social networks actually get this. The power of joining connected groups together is called the network effect, after all.